Structural, elastic, and electronic properties of chemically functionalized boron phosphide monolayer

Surface functionalization is one of the useful techniques for modulating the mechanical and electronic properties of two-dimensional systems. In the present study, we investigate the structural, elastic, and electronic properties of hexagonal boron phosphide monolayer functionalized by Br and Cl atoms using first-principles predictions. Once surface-functionalized with Br/Cl atoms, the planar structure of BP monolayer is transformed to the low-buckled lattice with the bucking constant of about 0.6 Å for all four configurations of functionalized boron phosphide,i.e., Cl-BP-Cl, Cl-BP-Br, Br-BP-Cl, and Br-BP-Br. The stability of functionalized BP monolayers is confirmedviatheir phonon spectra analysis andab initiomolecular dynamics simulations. Our calculations indicate that the functionalized BP monolayers possess a fully isotropic elastic characteristic with the perfect circular shape of the angle-dependent Young's modulus and Poisson's ratio due to the hexagonal symmetry. The Cl-BP-Cl is the most stiff with the Young's modulusC_2D= 43.234 N m⁻¹. All four configurations of the functionalized boron phosphide are direct semiconductors with a larger band gap than that of a pure BP monolayer. The outstanding stability, isotropic elastic properties, and moderate band gap make functionalized boron phosphide a very intriguing candidate for next-generation nanoelectromechanical devices.